Butene distribution

The activity of CoSx-MoSx/NaY (2. IMo/SC) is shown in Fig.5 for the HYD of butadiene as a function of the Co/Mo atomic ratio. The HYD activity decreased slightly on the addition of Co up to Co/Mo = ca. 1, followed by a steep decrease at a further incorporation of Co. The HYD/HDS activity ratio decreased with increasing Co content and reached the ratio for CoSx/NaY at the Co/Mo atomic ratio of the maximum HDS activity (Fig.3). The product selectivity in the HYD of butadiene shifted from t-2-butene rich distribution to 1-butene rich one on the addition of Co, as presented in Fig.6. It is worthy of noting that at the Co/Mo ratio of the maximum HDS activity, the butene distribution is close to that for CoSx/NaY. It should be noted, however, that these product distributions are not the initial distributions of the HYD over the catalyst but the distributions modified by successive isomerization reactions. It was found that MoSx/NaY showed high isomerization activities of butenes even in the... 

Figure 6. Butene distribution of the HYD of butadiene over CoSx-MoSx/NaY (2. IMo/ SC) as a function of the Co/Mo atomic ratio. O t-2-butene, cis-2-butene, 1-butene.

The hydrogenation of buta-1 2-diene appears to have received relatively little attention. Over palladium—alumina at room temperature, the products of the gas phase hydrogenation were c/s-but-2-ene, 52% but-l-ene, 40% frans-but-2-ene, 7% and n-butane, 1% [189]. Some isomerisation of the buta-1 2-diene to but-2-yne (10%) together with traces of but-l-yne and buta-1 3-diene was also observed. A similar butene distribution (namely, cis-but-2-ene 52%, but-l-ene 45% and frans-but-2-ene 3%) was observed in the liquid phase hydrogenation over palladium [186]. 

In the nickel- and cobalt-catalysed reactions [166,207] it was observed that the butene distribution depended upon the temperature of reduction of the catalyst. For both powders and alumina-supported catalysts prepared by reduction of the oxides, reduction at temperatures below ca. 330° C gave catalysts which exhibited so-called Type A behaviour where but-2-ene was the major product and the frans-but-2-ene/cis-but-2-ene ratio was around unity. Reduction above 360° C (Ni) or 440° C (Co) yielded catalysts which gave frans-but-2-ene as the major product (Type B behaviour). It is of interest to note that the yield of cis-but-2-ene was not significantly dependent upon the catalyst reduction temperature with either metal. 

Mechanism A is a generalised mechanism which was proposed for those metals where the frans-but-2-ene cis-but-2-ene ratio was around unity. This mechanism contains a variety of reversible steps which permit the conformational interconversion of the diadsorbed buta-1 3-diene. Consequently, the trans cis ratio will depend upon the relative rates of these reversible steps and the ratio may be much lower than would be expected if the relative surface concentrations of anti- and syn-diadsorbed buta-1 3-diene, species I and III, respectively, in Fig. 37, were similar to the relative amounts of anti- and syn-buta-1 3-diene in the gas phase. It was also suggested that the relative importance of the various steps in mechanism A may be different for different metals. Thus, for example, the type A behaviour of nickel and cobalt catalysts, as deduced from the butene distributions and a detailed examination of the butene AAprofiles [166], was... 

Zeolite supported Co-Mo composite catalysts were prepared by introducing Co(NO)(CO)3 or Mo(CO)6 into MoSx/NaY or CoSx/NaY, respectively, followed by a subsequent sulfidation at 673 K. Figure 12 shows the HDS activity of the composite catalyst, CoSx-MoSx/NaY (Co was introduced after Mo, 2 Mo/SC), as a function of the CoMo atomic ratio. It is revealed that the maximum activity is obtained around Co/Mo = 1. No activity decrease was observed even after prolonged sulfidation at 673 K. The HYD/HDS activity ratio decreased with increasing Co content and reached the ratio for CoSx/NaY at the composition where the maximum HDS activity is attained. In addition, the butene distribution in the butadiene HYD became identical with that of CoSx/NaY at Co/Mo = ca. 1. The HDS activity of MoSx-CoSx/NaY catalyst in which Mo was added to the pre-existing Co sulfide species was identical with that of CoSx-MoSx/NaY at the same composition. The HDS activity of MoSx/NaY, however, was remarkably decreased by the addition of Fe by using Fe(CO)s (FeSx-MoSx/NaY). 

Initial Butene Distributions and Selectivities Obtained in the Hydrogenation of 2-Butyne over Some Alumina-Supported... 

Precursor Initial butadiene hydrogenation rate [pmol/m2 s] Butene distribution Ratio Ratio but-l-ene trans- but-2-ene ... 

Table 9.1 Butene distributions obtained after the hydrogenation of butadiene over various metal catalysts.

Content of Ot-Olefin. An increase in the a-olefin content of a copolymer results in a decrease of both crystallinity and density, accompanied by a significant reduction of the polymer mechanical modulus (stiffness). Eor example, the modulus values of ethylene—1-butene copolymers with a nonuniform compositional distribution decrease as shown in Table 2 (6). A similar dependence exists for ethylene—1-octene copolymers with uniform branching distribution (7), even though all such materials are, in general, much more elastic (see Table 2). An increase in the a-olefin content in the copolymers also results in a decrease of their tensile strength but a small increase in the elongation at break (8). These two dependencies, however, are not as pronounced as that for the resin modulus. 

The effect of butene isomer distribution on alkylate composition produced with HF catalyst (21) is shown in Table 1. The alkylate product octane is highest for 2-butene feedstock and lowest for 1-butene isobutylene is intermediate. The fact that the major product from 1-butene is trimethylpentane and not the expected primary product dimethylhexane indicates that significant isomerization of 1-butene has occurred before alkylation. 

Isomerization. Isomerization of any of the butylene isomers to increase supply of another isomer is not practiced commercially. However, their isomerization has been studied extensively because formation and isomerization accompany many refinery processes maximization of 2-butene content maximizes octane number when isobutane is alkylated with butene streams using HF as catalyst and isomerization of high concentrations of 1-butene to 2-butene in mixtures with isobutylene could simplify subsequent separations (22). One plant (Phillips) is now being operated for this latter purpose (23,24). The general topic of isomerization has been covered in detail (25—27). Isomer distribution at thermodynamic equiUbrium in the range 300—1000 Kis summarized in Table 4 (25). 

In the peaking process of the Ethyl Corporation, the catalytic single-step process and the stoichiometric two-step process are combined. The result is an olefin mixture with a narrowed molecular weight distribution [25]. In this combined process low molecular weight olefins (preferably n-butene-1) obtained by a single-step process are used as displacement olefins (instead of ethylene) in the second step of the stoichiometric two-step Alfen process. Table 7 shows the composition of an olefinic mixture produced by the combination process of the Ethyl Corporation. The values in Table 7 show that the olefin mixtures of the... 

In the absence of considerations mentioned below, orientation is statistical and is determined by the number of p hydrogens available (therefore Hofmann s rule is followed). For example, sec-butyl acetate gives 55-62% 1-butene and 38-45% 2-butene, which is close to the 3 2 distribution predicted by the number of hydrogens available. ... 

The catalytic degradation of polypropylene was carried out over ferrierite catalyst using a thermogravimetric analyzer as well as a fixed bed batch reactor. The activation of reaction was lowered by adding ferrierite catalyst, which was similar with that from ZSM-5. Ferrierite produced less gaseous products than HZSM-5, where the yields of i-butene and olefin over ferrierite were higher than that over HZSM-5. In the case of liquid product, main product over ferrierite is C5 hydrocarbon, while products were distributed over mainly C7-C9 over HZSM-5. Ferrierite showed excellent catalytic stability for polypropylene degradation. 

The product distribution of the HDS of thiophene over the Mo(lOO) surface is shown in Table III compared with that reported by Kolboe over a MoS catalyst (14). It is clear that the two are very similar ana that our catalyst mimics the MoS catalyst very closely in this respect. An Arrhenius plot fpigure 2) made in the temperature region mentioned above shows that butadiene is the only product whose rate of formation shows true Arrhenius type dependence and yields an activation energy of 14.4 kcal/mole. At high temperatures the rate of butane formation deviates even more sharply than that of the butenes and does so at lower temperatures (9). 

Fig. 34. Sample TOF spectra for YC4H6 products at indicated lab angles for the Y + cis-2-butene reaction at fJcoii = 26.6 kcal/mol (open circles). Solid-line fits generated using CM distributions shown in Fig. 38.

---